C1D1 boundaries vs seal offs

[Edwarjw22]

I have been working on a sewer wet well installation. The wet well is defined as class 1 div 1 by NFPA820. The submersible pumps have a multiconductor cord that is sealed into the pump and extends from the wet well to a JB where it is terminated. This cord passes through a pipe, sleeve, conduit, whatever you want to call it that stops at grade level and is not sealed. The cable extends upward into an enclosure that has a class 1 div 2 cable gland fitting installed. This JB is mounted greater than 3 feet above the open pipe that passes into the well. From the JB we have rigid conduit with poured seal off fittings running to the MCP that is located greater than 5 feet from any well openings.

In my opinion the open pipe from the well, C1D1, extends that C1D1 classification to the opening of the pipe and as long as the boundary distances are met and we do not intend on extending the pipe outside of the boundary area, a poured seal off is not required. It is only required if we want to stop the C1D1 boundary distance.

According to NFPA820, 3 feet beyond any opening into the well is C1D1. Between 3 feet and 5 feet is C1D2 and beyond 5 feet is unclassified.

This has been a very long topic of discussion, and I would really like some input.

 

[Strathead]

I have been working on a sewer wet well installation. The wet well is defined as class 1 div 1 by NFPA820. The submersible pumps have a multiconductor cord that is sealed into the pump and extends from the wet well to a JB where it is terminated. This cord passes through a pipe, sleeve, conduit, whatever you want to call it that stops at grade level and is not sealed. The cable extends upward into an enclosure that has a class 1 div 2 cable gland fitting installed. This JB is mounted greater than 3 feet above the open pipe that passes into the well. From the JB we have rigid conduit with poured seal off fittings running to the MCP that is located greater than 5 feet from any well openings.

In my opinion the open pipe from the well, C1D1, extends that C1D1 classification to the opening of the pipe and as long as the boundary distances are met and we do not intend on extending the pipe outside of the boundary area, a poured seal off is not required. It is only required if we want to stop the C1D1 boundary distance.

According to NFPA820, 3 feet beyond any opening into the well is C1D1. Between 3 feet and 5 feet is C1D2 and beyond 5 feet is unclassified.

This has been a very long topic of discussion, and I would really like some input.

I don't know exactly, but using just your wording, 3 feet beyond is not the same thing as 3 feet above. But also, where you describe, the conduit is a sleeve not a "conduit" so I don't think any requirement to seal it would be in the NEC. It would be more about the types of gasses and the sealing of the boundaries. For being on the safe side, I would think an EYS fitting at the end of the chase would not be too difficult to alleviate concern.

 

[Edwarjw22]

NFPA820 refers to the boundary area around this opening as an envelope with a 3 foot radius. I believe that I did read that it included above. The issue is the EYS. The problem with it is that the pumps need to be readily serviceable in accordance with the 10 State Standards and the cables need to be able to be removed readily. So every time that you have to remove them the sealing compound has to be busted out and resealed. This causes issue because typically that material ends up down in the pipe and wedges the cable in the pipe. At that time you now need to dig up the pipe and rebuild things. That's not readily serviceable. This application is a sewer lift station.